DE102020204837A1 - Plate heat exchanger with locally varying thermal conductivity - Google Patents

Abstract

Disclosed is a heat exchanger, in particular for use in a distillation plant, having an installation frame and a base unit configured as a stack of several plates, the plates of the base unit having an embossing for forming fluid channels, with at least one fluid channel for guiding a fluid between at least two plates is formed, wherein the plates consist of a thermally conductive plastic, wherein at least one plate of the base unit has at least one area with a reduced thermal conductivity and at least one area with an increased thermal conductivity. Furthermore, a system for the thermal treatment of at least one fluid is disclosed.

Description

The invention relates to a heat exchanger, in particular for use in a distillation plant, having an installation frame and a base unit configured as a stack of several plates, the plates of the base unit having an embossing for forming fluid channels, with at least one fluid channel for guiding a fluid between at least two plates is formed. The invention also relates to a system with at least one such heat exchanger.

State of the art

In the manufacture of distillation systems, the heat exchanger is one of the most expensive components, as the heat exchanger is precisely tailored to the process of the respective distillation system, such as fresh water extraction. The heat exchanger can be designed as a combined evaporator and condenser.

Heat exchangers made of metal have good thermal conductivity, which is associated with an increased risk of fouling. Plastic heat exchangers or heat exchangers made from thermally conductive plastic are also known. Such heat exchangers made of plastic have a reduced risk of fouling, but are limited in terms of thermal conductivity.

When using heat exchangers made of metal, such as titanium or stainless steel, the risk of theft can increase because the metal can be melted and reused as required.

Disclosure of the invention

The object on which the invention is based can be seen in proposing a heat exchanger which combines the advantages of a heat exchanger made from a plastic with the advantages of a heat exchanger made from a metal.

This object is achieved by means of the respective subject matter of the independent claims. Advantageous refinements of the invention are the subject matter of the respective dependent subclaims.

According to one aspect of the invention, a heat exchanger, in particular for use in a distillation plant, is provided. The heat exchanger has an installation frame and a base unit configured as a stack of several plates, the plates of the base unit having an embossing in order to form fluid channels. At least one fluid channel is designed for guiding a fluid between at least two plates. The plates preferably consist of a thermally conductive plastic, at least one plate of the base unit having at least one area with reduced thermal conductivity and at least one area with increased thermal conductivity.

Such a heat exchanger has plates which include a local variation in the thermal conductivity. The thermal conductivity can be increased locally by introducing fillers and / or filler particles. In particular, areas with thermal insulation and areas with thermal conductivity can be created which avoid additional insulation by means of rubber coatings or silicone coatings.

The respective plates can be permanently connected to form a block or a base unit. Such plates can have bulges or embossments through which fluid channels are created between a plurality of stacked plates in order to conduct fluids parallel to and between the plates. The plates can preferably be produced by injection molding. The plastic or the polymer for producing the plates is introduced into a corresponding injection mold in such a way that the orientation of the filler particles is adjusted.

During the production of the plates, the thermal conductivity in injection molding can be controlled by suitable placement of the injection points. The alignment of the filler particles, which serve as conductive particles for the heat transport, and thus the thermal conductivity can thus be controlled locally. In this way, heat exchanger plates can be made insulating in the edge area, for example, while the thermal conductivity remains high in the area of the heat exchanger surface. Thermal insulation of the heat conducting plates, as is the case with a metal version, can therefore be omitted.

By using plates made of a plastic, the risk of fouling can be reduced and maintenance intervals can be extended. Furthermore, the heat exchanger can be manufactured in a technically simple and cost-effective manner by using plastic plates. Due to the local increase in thermal conductivity, the dimensions of the heat exchanger can be reduced compared to the use of a conventional thermally conductive polymer.

The heat exchanger can be used as a combined evaporator / condenser unit, as a Plate heat exchangers, a falling film evaporator and the like can be configured. The heat exchanger can also be used in vacuum processes or in vapor compression.

In one embodiment, the plates of the base unit are connected to one another in a fluid-tight manner at least on the circumferential side, each plate having at least one opening for guiding a fluid through the fluid channel. The at least one opening is connected to a fluid inlet and / or a fluid outlet of the base unit.

A peripheral edge of the plates is preferably designed as an edge region with reduced thermal conductivity. This measure eliminates the need to introduce additional thermal insulation at the edge of the panels. Such a heat exchanger can thus be produced more quickly and more cost-effectively.

According to a further embodiment, the edge region of the plates surrounds at least one central region of the plate on the circumferential side, the central region having a higher thermal conductivity than the edge region. As a result, the central area can be designed as a thermally active area with a high thermal conductivity. This can be implemented, for example, solely by the way in which the plastic is fed into the injection mold.

The edge area preferably remains less thermally conductive. Alternatively or additionally, the edge area can be designed without filler particles, so that the edge area remains thermally insulating. This enables quick start-stop behavior for decentralized use for drinking water production.

The plates are preferably designed as thin, contoured elements. The contours form embossments and thus the cross-sectional shapes for the at least one fluid channel. Openings are made in the plates, which serve as feeds of at least one fluid into the at least one fluid channel.

The filler particles can for example consist of a metal or of carbon. In particular, the thermal conductivity can be set by aligning the filler particles during molding, injection molding or deep drawing or during the curing of the plastic in an injection mold. Due to the increased thermal conductivity of the filler particles compared to the polymer, when filler particles are used which have a longer and at least one shorter length in the projection, an anisotropic thermal conductivity of the plates or of the cured material is established. A heat transport through or along the plate essentially follows the alignment of the filler particles. For example, the thermal conductivity can be maximized if the filler particles form contact bridges between both sides of the plate.

According to one embodiment, the plates of the base unit have the same arrangement or a different arrangement of the areas with reduced thermal conductivity and the areas with increased thermal conductivity. As a result of this measure, the plates of the base unit can be designed to be the same or different. Targeted control of the thermal conductivity and the performance of the base unit is thus possible. In particular, individual plates of the base unit can have a varying thermal conductivity distribution and individual plates can have a constant thermal conductivity distribution. In a further embodiment, all plates can have a varying thermal conductivity distribution.

According to a further embodiment, the plates of the base unit are glued or welded to one another on the circumferential side. As a result, the base unit of the heat exchanger is designed as an integral block.

Due to the optimized thermal conductivity distribution of the plates of the base unit, the performance and the size of the system can be designed to be comparable to that of a metallic heat exchanger. At the same time, the tendency to fouling and the weight of the heat exchanger can be reduced by up to a third. In this way, the heat transfer, especially when designed as an interchangeable part with universal connections, can be easily expanded and cleaned externally.

According to one embodiment, the plates of the base unit are made from a thermally conductive polymer, such as PVDF, PE, PVC, PVCC, PP or PFA, with at least one filler in the form of filler particles. This allows the plates to be manufactured as an injection-molded part. A targeted control of the filler particle density and the alignment of the filler particles is possible, which enables a control of the local thermal conductivity along a flat extension of the plates.

Furthermore, base units made of a thermally conductive polymer are not attractive to thieves and thus enable particularly safe operation.

According to a further embodiment, the thermal conductivity of the areas of the plates of the base unit can be adjusted by aligning filler particles and / or a filler particle density. In particular, the filler particles can be used to form contact bridges between them in order to achieve high thermal conductivity. The absence of filler particles can be used to form thermally insulating areas. The fill particle density can therefore also be 0 in order to achieve a high level of thermal insulation.

Alternatively or additionally, filler particles to increase the thermal conductivity and / or filler particles to reduce the thermal conductivity can be introduced locally into the injection mold during the injection molding process in order to form a varying distribution of thermal conductivity along the plates.

According to one embodiment, fluid channels for guiding a heating fluid, fluid channels for guiding a fluid to be condensed and fluid channels for guiding a cooling fluid are formed between the plates of the base unit, the fluid channels for guiding the heating fluid and the fluid channels for guiding the cooling fluid through at least one area with less Thermal conductivity are spaced from each other. This can be advantageous, for example, in a heat exchanger in which a drinking water vapor is condensed in one section, droplet separation is to take place in an intermediate section and heating to form the drinking water vapor is carried out in one section. The intermediate section can thus have a reduced thermal conductivity in order to increase the efficiency of the heat exchanger and to achieve an optimal separation of the processes.

In a further embodiment, the base unit and / or the plates of the base unit are arranged in the installation frame by screw connections or by quick-release connections. If the plates are sealed as a block or as a base unit, the block can be connected to a distillation plant at the entry and exit points for the fluids in a technically simple manner by means of circumferential seals. As a result, no high pretensioning forces and no heavy plates of the installation frame are required.

Due to the low weight of the heat exchanger, dismantling can be carried out more easily and quickly. This also simplifies external cleaning of the heat exchanger.

According to a further aspect of the invention, a system for the thermal treatment of at least one fluid is provided. The system can be designed, for example, as a drinking water distillation system and has at least one heat exchanger according to the invention. The heat exchanger preferably has a base unit made from at least one thermally conductive polymer in some areas, which is designed for the temperatures of the at least one fluid of the system.

The system can, for example, be suitable for water treatment for local drinking water production with a franchise concept. Furthermore, the operating time of the system can be maximized, since the built-in heat exchanger can be exchanged for a replacement heat exchanger if necessary. The system downtime is limited to exchanging the heat exchanger. Furthermore, the removal and installation of the heat exchanger can be simplified and accelerated due to the lower weight of the heat exchanger. Tamper protection can be implemented by precisely coordinating the heat exchanger with the system with regard to the temperatures used.

If the output of the system is to be increased, for example with an increasing number of customers and the resulting water requirement, a system operator can upgrade the system by installing a thermally optimized base unit and / or heat exchanger. A thermally optimized heat exchanger has plates which comprise a thermal conductivity distribution with areas of low thermal conductivity and with areas of higher thermal conductivity. This can improve the efficiency of the heat exchanger and increase the resulting drinking water turnover.

If the system or the plant is designed for the thermal properties of the filled polymer of the plates at nominal output, the plant only works with this block or this basic unit of the heat exchanger. Replicas or plagiarisms cannot reach the fresh water production rate if they are made from an alternative polymer.

According to one embodiment, the heat exchanger is designed as a plate heat exchanger or as a falling film evaporator in plate construction. As a result, the heat exchanger can be used flexibly in differently designed systems. By producing the plates of the heat exchanger in an injection molding process and a subsequent connecting step of the plates, any desired shapes and fluid channel arrangements can be realized for different applications.

According to a further embodiment, the system can be operated with at least one first heat exchanger made of a plastic, the first heat exchanger being exchangeable by a heat exchanger according to the invention designed as an exchangeable part. As a result, the heat exchanger can be designed as an interchangeable part to increase performance. The system can be from The basic concept should be designed for a polymer heat exchanger which is not thermally optimized and thus has a constant thermal conductivity distribution. This first heat exchanger can be replaced by a thermally optimized heat exchanger to increase performance in order to increase performance.

• 1 eine schematische Darstellung einer Anlage gemäß einer Ausführungsform,
• 2,3 schematische Querschnitte eines Wärmetauschers gemäß einer Ausführungsform,
• 4 eine Explosionsdarstellung eines Wärmetauschers gemäß einem weiteren Ausführungsbeispiel und
• 5 schematische Detailansichten eines Bereichs mit einer verringerten Wärmeleitfähigkeit und eines Bereichs mit einer erhöhten Wärmeleitfähigkeit.

In the following, preferred exemplary embodiments of the invention are explained in more detail on the basis of greatly simplified schematic representations. Show here

• 1 a schematic representation of a system according to an embodiment,
• 2 , 3 schematic cross-sections of a heat exchanger according to an embodiment,
• 4th an exploded view of a heat exchanger according to a further embodiment and
• 5 schematic detailed views of an area with a reduced thermal conductivity and an area with an increased thermal conductivity.

the 1 shows a schematic representation of a plant 1 according to one embodiment. The attachment 1 is designed, for example, as a drinking water treatment plant or distillation plant, which extracts drinking water from salt water by distillation. The attachment 1 has a heat exchanger 2 on.

The heat exchanger 2 has a base unit 4th on. The base unit 4th is in a mounting frame 6th , 8th used and consists of a large number of plates 5 . Through the plates 5 become fluid channels 7th formed, which parallel to a flat extension of the plates 5 get lost. In particular, between two plates 5 one or more fluid channels 7th be provided. The fluid channels 7th are used to guide fluids such as steam or water.

The plates 5 are made from at least one polymer. The polymer of the plates 5 can be provided with filler particles at least in some areas in order to achieve a targeted local variation of the thermal conductivity.

The base unit 4th is exchangeable in the installation frame 6th , 8th arranged. For example, the base unit 4th in the mounting frame 6th , 8th be screwed or clamped by tension hooks.

The installation frame 6th , 8th has a connection section 6th and a counter section 8th on, between which the base unit 4th is arranged. The fluid channels 7th the base unit 4th are in the illustrated embodiment fluid-carrying with connections 10 , 11 , 12th , 13th , 14th , 15th of the connection section 6th tied together.

The connections 10 , 11 , 12th , 13th , 14th , 15th of the connection section 6th are for example as a connector 10 for salt water supply, one connection 11 for the drainage of the brine, a connection 12th for discharging the drinking water vapor, one connection 13th for heating steam supply, one connection 14th for a heating steam return and a connection 15th designed for a condensate return of the heating steam.

For example, it can be a fluid channel 7th can be used to conduct heating steam. An adjacent fluid channel 7th can get salt water from the salt water supply 10 lead and thus heat to boiling temperature. The resulting drinking water vapor can pass through the connection 12th for the drinking water vapor to escape and in a condenser 16 be liquefied. The liquefied drinking water can then be stored in a collecting tank 18th be caught.

The heating steam can with the help of a steam generator 19th generated and via the connector 13th for heating steam in the heat exchanger 2 reach. The one from the heat exchanger 2 Leaking heating steam and the condensate of the heating steam can be connected via the corresponding connections 14th , 15th the steam generator again 19th are fed.

In the 2 and the 3 are schematic cross-sections of the heat exchanger 2 shown according to one embodiment. The heat exchanger 2 has a base unit 4th on which of several panels 5 is made. The plates 5 are welded together on the circumference so that the base unit 4th is formed as an integrally continuous block. The block or the base unit 4th is between the connection section 6th and the counter section 8th clamped in the mounting frame.

In the 4th is an exploded view of the heat exchanger 2 to illustrate the structure of the heat exchanger 2 and the arrangement of the base unit 4th shown.

The plates 5 the base unit 4th are connected to one another in a fluid-tight manner, at least on the circumferential side. Any plate 5 has openings 20th , 22nd , 23 , 25th for guiding fluids through the at least one fluid channel 7th on. The openings 20th , 22nd , 23 , 25th are with corresponding fluid inlets 10 , 13th and fluid outlets 12th , 15th fluidly connected.

A peripheral edge 30th of the plates 5 is as an edge area 30th designed with reduced thermal conductivity. The edge area 30th is made, for example, from a polymer without the addition of filler particles and preferably has a thermally insulating effect.

The edge area 30th of the plates 5 according to the exemplary embodiment, surrounds a central area on the circumferential side 32 . The central area 32 corresponds to an area 32 with an increased thermal conductivity and has a opposite to the edge area 30th increased thermal conductivity. The central area 32 can preferably have filler particles which were additionally injected locally into the polymer during an injection molding process in order to enable improved heat transport.

The polymer of the plates 5 can for example be PVDF, PE, PVC, PVCC, PP or PFA.

In the 4th is the central area 32 through an additional area 30th subdivided with reduced thermal conductivity, for example around the heating steam supply 13th from other connections 10 , 12th , 15th to be thermally separated.

the 5 shows schematic detailed views of an area 30th with a reduced thermal conductivity and area 32 with an increased thermal conductivity. It is illustrated that filler particles 34 for forming contact bridges 36 can be used to achieve high thermal conductivity. The absence of filler particles 34 can be used to form thermally insulating areas 30th can be used. The fill particle density can therefore also be 0 in order to achieve a high level of thermal insulation.

By introducing filler particles 34 and aligning the filler particles 34 can contact bridges 36 which can increase or maximize the thermal conductivity.

Claims (12)

Heat exchanger (2), in particular for use in a distillation plant, having an installation frame (6, 8) and a base unit (4) configured as a stack of several plates (5), the plates (5) of the base unit (4) for Forming fluid channels (7) have an embossing, wherein at least one fluid channel (7) is designed for guiding a fluid between at least two plates (5), characterized in that the plates (5) consist of a thermally conductive plastic, with at least one plate (5) the base unit (4) has at least one area (30) with a reduced thermal conductivity and at least one area (32) with an increased thermal conductivity. Heat exchanger after Claim 1 , wherein the plates (5) of the base unit (4) are connected to one another in a fluid-tight manner at least on the circumferential side, each plate (5) having at least one opening (20, 22, 23, 25) for guiding a fluid through the fluid channel (7), wherein the at least one opening (20, 22, 23, 25) is connected to a fluid inlet (10, 13) and / or a fluid outlet (12, 15) of the mounting frame (6, 8), a peripheral edge of the plates (5) is designed as an edge region (30) with reduced thermal conductivity. Heat exchanger after Claim 1 or 2 wherein the edge region (30) of the plates (5) surrounds at least one central region (32) on the circumferential side, the central region (32) having a higher thermal conductivity than the edge region (30). Heat exchanger after one of the Claims 1 until 3 wherein the plates (5) of the base unit (4) have the same arrangement or a different arrangement of the areas (30) with reduced thermal conductivity and the areas (32) with increased thermal conductivity. Heat exchanger after one of the Claims 1 until 4th , the plates (5) of the base unit (4) being glued or welded to one another on the circumferential side. Heat exchanger after one of the Claims 1 until 5 wherein the plates (5) of the base unit (4) are made from a thermally conductive polymer, such as PVDF, PE, PVC, PVCC, PP or PFA, with at least one filler in the form of filler particles (34). Heat exchanger after one of the Claims 1 until 6th wherein the thermal conductivity of the areas (30, 32) of the plates (5) of the base unit (4) can be adjusted by an alignment of filler particles (34) and / or a filler particle density. Heat exchanger after one of the Claims 1 until 7th , wherein fluid channels (7) for guiding a heating fluid, fluid channels (7) for guiding a fluid to be condensed and fluid channels (7) for guiding a cooling fluid are formed between the plates (5) of the base unit (4), the fluid channels (7) for guiding the heating fluid and the fluid channels (7) for guiding the cooling fluid through at least one region (30) with low thermal conductivity are spaced apart from one another. Heat exchanger after one of the Claims 1 until 8th , wherein the base unit (4) and / or the plates (5) of the base unit (4) are arranged in the mounting frame (6, 8) by screw connections or by quick-release connections. Plant (1) for the thermal treatment of at least one fluid, the plant (1) having at least one heat exchanger (2) according to one of the has preceding claims, wherein the heat exchanger (2) has a base unit (4) made of at least one thermally conductive polymer in some areas, which is designed for the temperatures of the fluid of the system (1). Plant after Claim 10 , wherein the heat exchanger (2) is designed as a plate heat exchanger or as a falling film evaporator in plate construction. Plant after Claim 10 or 11 , wherein the system (1) can be operated with at least one first heat exchanger made of a plastic, wherein the first heat exchanger by a heat exchanger (2) designed as a replacement part according to one of the Claims 1 until 9 is interchangeable.

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